1. Field of the Invention
The present invention relates to a method for determining a distance of visibility for a driver of a vehicle in the presence of an element disrupting the visibility of the driver. The disruptive element is for example fog and the vehicle, a motor vehicle for example.
2. Description of the Related Art
According to a known prior art EP 1 422 663 A1, such a method of determination comprises the following steps:                videoing at least one image of a field of space located in front of the vehicle, the image being defined by an array of pixels,        separating the image in two parts by a line passing through a pre-set point,        determining the luminosity of the pixels of the line, resulting in a curve of luminosity,        determining an inflection point of the luminosity curve by calculating the derivative of the curve,        determining the distance of visibility of the driver of the vehicle according to the position of the inflection point on the image.        
Such a solution presents the following disadvantages.
Firstly calculation of the derivative leads to problems in interpretation, significant inaccuracies and errors, particularly if there is an obstacle on the road over which a vehicle is travelling, for example another vehicle, a bridge and the like. Indeed such an obstacle will generate a plurality of points of inflection when calculating the derivative, hence the difficulty in distinguishing the various points of inflection if they are close to one another and in choosing the good inflection point corresponding to the distance of visibility searched.
Secondly the calculation of the derivative amplifies the noise generated on the luminosity curve causing uncertainties on the curve itself.
Lastly calculation of the derivative represents a heavy computational load.
What is needed, therefore, is an improved system and method that provides improvements over prior art systems and methods.